A contribution to the understanding of cavitation effects in Diesel injector nozzles through a combined experimental and computational investigation

Payri, F.; Payri, Raúl; Salvador, Francisco; Martinez-Lopez, J I

doi:10.1016/j.compfluid.2012.01.005

Cited by 94 publications

(81 citation statements)

References 34 publications

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“…The effect of increased injection pressure, which increased spray velocity/momentum [21], is more noticeable in the transient part of the liquid spray penetration than the quasi steady stage. The slight positive slope observed at the steady period in some of the liquid penetration curves in Figures 4 and 5 can be attributed to two factors [8,17]. Firstly, the temperature of the fuel at the beginning of the injection is higher because the injector sac is always in direct contact with the high temperature gas of the combustion chamber; during the injection, the fuel flowing from upstream of the sac cools down the injector tip.…”

Section: Resultsmentioning

confidence: 99%

“…The analyses of injection system development have been presented from several viewpoints. Nozzle geometry has been studied for the influence on the internal flow and spray characteristics with respect to: atomization [4,5], mixing processes [6,7], emission [9,10] and cavitation [8,13]. Different injection strategies have been investigated to show the effect on pollutant emissions [2,3].…”

Section: Introductionmentioning

confidence: 99%

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Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.

Njere

Emekwuru

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The evolution of diesel fuel injection technology, to facilitate strong correlations of in-cylinder spray propagation with injection conditions and injector geometry, is crucial in facing emission challenges. More observations of spray propagation are, therefore, required to provide valuable information on how to ensure that all the injected fuel has maximum contact with the available air, to promote complete combustion and reduce emissions. In this study, high pressure diesel fuel sprays are injected into a constant-volume chamber at injection and ambient pressure values typical of current diesel engines. For these types of sprays the maximum fuel liquid phase penetration is different and reached sooner than the maximum fuel vapour phase penetration. Thus, the vapour fuel could reach the combustion chamber wall and could be convected and deflected by swirling air. In hot combustion chambers this impingement can be acceptable but this might be less so in larger combustion chambers with cold walls. The fuel-ambient mixture in vapourized fuel spray jets is essential to the efficient performance of these engines. For this work, the fuel vapour penetration values are presented for fuel injectors of different k-factors. The results indicate that the geometry of fuel injectors based on the k-factors appear to affect the vapour phase penetration more than the liquid phase penetration. This is a consequence of the effects of the injector types on the exit velocity of the fuel droplets. KeywordVapour, spray, k-factor, shadowgraph. IntroductionSpray formation occurs with the introduction of liquid into a gaseous environment through an orifice such that the liquid breaks-up into droplets by interacting with the surrounding gases and causing its own unsteadiness [3]. For diesel engines, spray characteristics (liquid/vapour penetration and distribution) significantly affect the combustion and emission processes. By optimizing these characteristics, the tailpipe emissions, mainly oxides of Nitrogen (NOx) and partciculate matter (PM), can be minimized [2]. Spray penetration, which is usually analysed macroscopically, considers the development of the liquid and vapour components. It is desirable to achieve optimal travel of these spray components to avoid the adverse effects of impingement caused by under/overpenetration of liquid spray [19,20]. Advances in fuel injection system, with the introduction of the common rail technology, have provided increased controllability of the injection event. The analyses of injection system development have been presented from several viewpoints. Nozzle geometry has been studied for the influence on the internal flow and spray characteristics with respect to: atomization [4,5], mixing processes [6,7], emission [9,10] and cavitation [8,13]. Different injection strategies have been investigated to show the effect on pollutant emissions [2,3]. Specific studies have also been conducted with conical and cylindrical nozzles [11,12], and to develop more understanding on the effects of nozzl...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.

Njere

Emekwuru

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

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“…The mass flow rate under choking conditions is controlled by the pressure drop between the upstream reservoir (p 1 ) and the section in which cavitation appears (p v ), while it is not correlated well with the pressure drop (p 1 − p 2 ) over the nozzle [39].…”

Section: Physics Of Cavitation and Comparison With Supersonic Flowsmentioning

confidence: 99%

“…The characterization provided for the choked flow, due to cavitation, theoretically makes this kind of regime clearly distinct from cavitation inception and supercavitation, even though the hydraulic criteria used to detect cavitation inception are often based on the detection of mass flow choking [39], or are empirically expressed in terms of a certain percentage reduction in the flow rate compared with the choking conditions [121,122]. On the other hand, the instability that occurs in transitional cavitation, within the L cav /L ≈ 0.25-0.35 range (see §3), makes it practically difficult to distinguish between the condition at which cavitation spreads over a critical section (choking) and the condition at which cavitation reaches the nozzle exit (supercavitation).…”

Section: Physics Of Cavitation and Comparison With Supersonic Flowsmentioning

confidence: 99%

“…Furthermore, the governing partial differential equations of the model can be arranged in dimensionless form, in order to exploit the advantages of hydrodynamic similarity. However, two-dimensional and three-dimensional computation approaches to cavitation are not yet at a fully mature stage, as the single-phase calculations of acoustic cavitation instead are, and they still need improvements and practice in order to increase confidence in the results [39].…”

Section: Introductionmentioning

confidence: 99%

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Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Ferrari¹

2017

Proc. R. Soc. A.

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Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and twophase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

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Numerical Study on the Effect of Cavitation on Flow and Diesel Fuel Atomization Characteristics

2013

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Computational fluid dynamics (CFD) models based on the turbulent mixture multiphase model were applied to consider the effect of cavitation on the spray of diesel fuel. The effects of injection pressure and length‐to‐width (L/W) ratio on the velocity distribution, cavitation number, discharged coefficient, and nozzle exit velocity were investigated and the performance of the model was compared with the experimental data. The results indicate that the cavitation generated in the nozzle has a strong impact on the fuel injection and spray quality, whereas the L/W ratio is a highly effective parameter for cavitation behavior. In addition, by increasing the L/W ratio, the range of cavitation number, wall friction, and flow resistance increase but in the cavitation region the velocity profile in radial and axial directions, spray cone angle, nozzle exit velocity, and the discharged coefficient decrease.

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A contribution to the understanding of cavitation effects in Diesel injector nozzles through a combined experimental and computational investigation

Cited by 94 publications

References 34 publications

Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.

Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Numerical Study on the Effect of Cavitation on Flow and Diesel Fuel Atomization Characteristics

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